Effect of particles on the photodegradation of PAHs in natural waters-A case study for the Yellow River     

Xinghui XIA 《中国地球化学学报》2006,25(B08):263-263

Photodegradation of chrysene, benzo （a） pyrene and benzo （g, h, i） perylene in natural water of the Yellow River was studied using simulation sunlight. The effects of particulates on the photodegradation were explored. Several results arose from this study. （1） The photodegradation of PAHs can be fitted with first-order kinetics when no particulate exists in water system, and the first-order constant increases with decreasing of initial concentration of PAHs. The photodegradation rates of the three PAHs are related to their molecule absorption spectrum. （2） The existence of loess exerts two kinds of effects on the photodegradation of PAHs, including the inner filter effects and the photosensitizing effects of humic substance in loess. These two contrary effects lead to the difference of net effects among different contents of loess. When the loess contents are 0.1 and 5.0 g/L, the existence of loess stimulates the photodegradation of chrysene, benzo （a） pyrene. When the loess content is 5.0 g/L, the existence of loess stimulates the photodegradation of benzo （g, h, i） perylene. In addition, the photodegradation of PAHs can be fitted with the second-order kinetics when there is loess in the water system. （3） The soluble humic substances in loess can accelerate the photodegradation of PAHs while the in soluble part cannot. （4） Since the soluble humic substances in the suspended solids of the river have been dissolved in water,  相似文献   

Stratigraphic evolution of a fluvial–eolian succession: The example of the Upper Jurassic—Lower Cretaceous Guará and Botucatu formations, Paraná Basin, Southernmost Brazil     

Claiton M.S. Scherer  Ernesto L.C. Lavina 《Gondwana Research》2006,9(4):475-484

The Guará and Botucatu formations comprise an 80 to 120 m thick continental succession that crops out on the western portion of the Rio Grande do Sul State (Southernmost Brazil). The Guará Formation (Upper Jurassic) displays a well-defined facies shift along its outcrop belt. On its northern portion it is characterised by coarse-grained to conglomeratic sandstones with trough and planar cross-bedding, as well as low-angle lamination, which are interpreted to represent braided river deposits. Southwards these fluvial facies thin out and interfinger with fine- to medium-grained sandstones with large-scale cross-stratification and horizontal lamination, interpreted as eolian dune and eolian sand sheets deposits, respectively. The Botucatu Formation is characterised by large-scale cross-strata formed by successive climbing of eolian dunes, without interdune and/or fluvial accumulation (dry eolian system). The contact between the Guará and the Botucatu formations is delineated by a basin-wide deflation surface (supersurface). The abrupt change in the depositional conditions that took place across this supersurface suggests a major climate change, from semi-arid (Upper Jurassic) to hyper-arid (Lower Cretaceous) conditions. A rearrangement of the Paraná Basin depocenters is contemporaneous to this climate change, which seems to have changed from a more restrict accumulation area in the Guará Formation to a wider sedimentary context in the Botucatu Formation.  相似文献   

Preparation of a geotechnical microzonation model using Geographical Information Systems based on Multicriteria Decision Analysis   总被引：3，自引：0，他引：3  

a&#x;l Kolat  Vedat Doyuran  Can Ayday  M. Lütfi Süzen 《Engineering Geology》2006,87(3-4):241-255

The purpose of this study is to develop a geotechnical microzonation model using Geographical Information Systems (GIS) based on Multicriteria Decision Analysis (MCDA). As study area, the Eskişehir downtown area has been chosen. Eskişehir is one of the most rapidly growing cities in central Turkey. The model inputs include slope, flood susceptibility, soil, depth to groundwater table, swelling potential, and liquefaction potential. The weight and rank values are assigned to the layers and to the classes of each layer respectively. The assignment of the weight/rank values and the analysis are realized by the application of two different decision models, namely Simple Additive Weighting (SAW) and Analytic Hierarchy Process (AHP) methods. The geotechnical microzonation maps prepared as outputs of these methods are found to be consistent with each other and confirmed by the experts within the study area. The geotechnical microzonation map prepared using the AHP method is recommended as the final map of the study.  相似文献   

Mineralogical and chemical transformation of Oldoinyo Lengai natrocarbonatites, Tanzania     

Anatoly N. Zaitsev  Jrg Keller 《Lithos》2006,91(1-4):191-207

The minerals of Oldoinyo Lengai natrocarbonatite lavas are unstable under atmospheric conditions. Subsolidus mineral assemblages in natrocarbonatites were studied in 105 samples from contemporary eruptions ranging from present day to about 100 years old. The subsolidus minerals in natrocarbonatites were formed (i) along cracks on the lava surface from hot gases escaping during cooling, (ii) as atmospheric alteration by solution of water-soluble minerals, in particular halides and gregoryite, and by hydration of nyerereite under the influence of meteoric water and (iii) by reaction with fumarole gases. After solidification, the lavas were cut by a network of thin cracks, the edges of which are covered by polymineralic encrustations. Samples collected 2–24 h after eruption contain nahcolite, trona, sylvite, and halite with accessory kalicinite and villiaumite. Atmospheric humidity results immediately (≥ 2 h after eruption) in alteration of black lavas that is marked by the appearance of white powdery thermonatrite with nahcolite on the lava surface. Subsequent reaction (weeks, months, years) of natrocarbonatite with meteoric water and the atmosphere results in the formation of pirssonite, gaylussite, shortite, trona, thermonatrite, nahcolite and calcite. Generally, the first important step is the formation of pirssonite and the end-members are calcite carbonate rocks or loose aggregates. Fumarolic activity is common for the active northern crater of the volcano. Reaction of hot (54–141 °C) fumarolic gases with natrocarbonatite leads to the formation of sulphur, gypsum, calcite, anhydrite, monohydrocalcite, barite and celestine. Changes in mineralogy of the natrocarbonatite lead to substantial chemical transformation. The most obvious chemical changes in this process are the loss of Na, K, Cl and S, combined with an increase in H₂O, Ca, Sr, Ba, F and Mn. The oxygen and carbon isotopic composition of altered natrocarbonatites shows a significant shift from the primary “Lengai Box” to high values of δ¹⁸O and δ¹³C. Calcite exhibits δ¹³C values between − 2‰ and − 4‰ PDB and δ¹⁸O values of + 23‰ to + 26‰ SMOW. The observed assemblages of secondary minerals formed by reaction with atmosphere and meteoric water, the changes in chemical composition of the natrocarbonatite and field observations suggest that alteration of natrocarbonatite is an open-system low-temperature process. It takes place at temperatures between 8 and 43 °C with the addition of H₂O to the system and the removal of Na, K, Cl and S from the carbonatites. Low-temperature thermodynamic models developed for alkali carbonate systems can be used for the interpretation of Oldoinyo Lengai subsolidus mineralization.  相似文献   

Heavy metals in freshly deposited sediments of the river Subernarekha, India: an example of lithogenic and anthropogenic effects   总被引：1，自引：0，他引：1  

A. K. Upadhyay  K. K. Gupta  J. K. Sircar  M. K. Deb  G. L. Mundhara 《Environmental Geology》2006,50(3):397-403

Heavy metal distribution patterns in river sediments aid in understanding the exogenic cycling of elements as well as in assessing the effect of anthropogenic influences. In India, the Subernarekha river flows over the Precambrian terrain of the Singhbhum craton in eastern India. The rocks are of an iron ore series and the primary rock types are schist and quartzite. One main tributary, the Kharkhai, flows through granite rocks and subsequently flows through the schist and quartzite layers. The Subernarekha flows through the East Singhbhum district, which is one of India’s industrialised areas known for ore mining, steel production, power generation, cement production and other related activities. Freshly deposited river sediments were collected upstream and downstream the industrial zone. Samples were collected from four locations and analysed in <63-μm sediment fraction for heavy metals including Zn, Pb, Cd and Cu by anodic stripping voltammetry. Enrichment of these elements over and above the local natural concentration level has been calculated and reported. Sediments of the present study are classified by Muller’s geo-accumulation index (I _geo) and vary from element to element and with climatic seasons. During pre-monsoon period the maximum I _geo value for Zn is moderately to highly polluted and for Cu and Pb is moderately polluted, respectively, based on the Muller’s standard. Anthropogenic, lithogenic or cumulative effects of both components are the main reasons for such variations in I _geo values. The basic igneous rock layer through which the river flows or a seasonal rivulet that joins with the main river may be the primary source for lithogenic components.  相似文献   

Magnitudes, spatial scales and processes of environmental antimony mobility from orogenic gold–antimony mineral deposits, Australasia     

P. M. Ashley  D. Craw  M. K. Tighe  N. J. Wilson 《Environmental Geology》2006,51(4):499-507

Antimony (Sb) is strongly concentrated into hydrothermal mineral deposits, commonly with gold, in metasedimentary sequences around the Pacific Rim. These deposits represent potential point sources for Sb in the downstream environment, particularly when mines are developed. This study documents the magnitude and scale of Sb mobility near some mineral deposits in Australia and New Zealand. Two examples of New Zealand historic mining areas demonstrate that natural groundwater dissolution of Sb from mineral deposits dominates the Sb load in drainage waters, with Sb concentrations between 3 and 24 μg/L in major streams. Mine-related discharges can exceed 200 μg/L Sb, but volumes are small. Sb flux in principal stream waters is ca 1–14 mg/s, compared to mine tunnel fluxes of ca 0.001 mg/s. Dissolved Sb is strongly attenuated near some mine tunnels by adsorption on to iron oxyhydroxide precipitates. Similar Sb mobilisation and attenuation processes are occurring downstream of the historic/active Hillgrove antimony–gold mine of New South Wales, Australia, but historic discharges of Sb-bearing debris has resulted in elevated Sb levels in stream sediments (ca 10–100⁺ mg/kg) and riparian plants (up to 100 mg/kg) for ca 300 km downstream. Dissolution of Sb from these sediments ensures that river waters have elevated Sb (ca 10–1,000 μg/L) over that distance. Total Sb flux reaching the Pacific Ocean from the Hillgrove area is ca 8 tonnes/year, of which 7 tonnes/year is particulate and 1 tonne/year is dissolved.  相似文献   

Groundwater study using remote sensing and geographic information systems (GIS) in the central highlands of Eritrea   总被引：3，自引：1，他引：3  

Semere Solomon  Friedrich Quiel 《Hydrogeology Journal》2006,14(6):1029-1041

Remote sensing, evaluation of digital elevation models (DEM), geographic information systems (GIS) and fieldwork techniques were combined to study the groundwater conditions in Eritrea. Remote sensing data were interpreted to produce lithological and lineament maps. DEM was used for lineament and geomorphologic mapping. Field studies permitted the study of structures and correlated them with lineament interpretations. Hydrogeological setting of springs and wells were investigated in the field, from well logs and pumping test data. All thematic layers were integrated and analysed in a GIS. Results show that groundwater occurrence is controlled by lithology, structures and landforms. Highest yields occur in basaltic rocks and are due to primary and secondary porosities. High yielding wells and springs are often related to large lineaments, lineament intersections and corresponding structural features. In metamorphic and igneous intrusive rocks with rugged landforms, groundwater occurs mainly in drainage channels with valley fill deposits. Zones of very good groundwater potential are characteristic for basaltic layers overlying lateritized crystalline rocks, flat topography with dense lineaments and structurally controlled drainage channels with valley fill deposits. The overall results demonstrate that the use of remote sensing and GIS provide potentially powerful tools to study groundwater resources and design a suitable exploration plan.The online version of the original article can be found at  相似文献   

Effect of a submerged bay-mouth breakwater on tsunami behavior analyzed by 2D/3D hybrid model simulation     

Koji Fujima 《Natural Hazards》2006,39(2):179-193

The hybrid numerical model had been developed to simulate a complicated 3D flow around structures generated by tsunami. In the model, the conventional 2D model is adopted for the wide region far from structures and the 3D non-hydrostatic pressure model is used in the limited region adjacent to structures. The applicability of the model is shown by comparisons of the numerical results with the experimental results of the laboratory model tests and the numerical analysis results of the conventional whole 2D simulation. In addition, the effect of a submerged structure at the opening of a breakwater is discussed from the numerical simulations by the hybrid model. The submerged structure improves the stability of the rubble mound and reduces the tsunami inflow into the bay, while it increases the water surface velocity around the opening of the breakwater. The increase of surface velocity causes the increases of impulsive forces by collision with drafts and so on.  相似文献   

Water–rock interaction during the process of steam stimulation exploitation of viscous crude oil in Liaohe Shuguang Oil Field, Liaoning, China     

Qian Hui  Yang Zhenghua  Li Yunfeng  Xu Wancai  Sun Yaqiao 《Environmental Geology》2006,50(2):229-236

In the process of steam stimulation exploitation of viscous crude oil, the injected water, at high temperature and under high pressure, reacts intensively with the host rock. This kind of water–rock interaction in Liaohe Shuguang Oil Field was studied on the basis of analysis of water composition changes, laboratory experiments, mineral saturation indices analysis, and mass balance calculation. Compared with the injected water, the changes of the composition of discharged water are mainly the distinct decrease of pH, Na⁺, SiO₂ and Cl⁻, as well as the increase of K⁺, Ca²⁺, Mg²⁺, SO ₄ ²⁻ and HCO ₃ ⁻ . Laboratory experiments under field conditions showed: the dissolution sequence of minerals quantitatively is quartz>potassium feldspar>albite, and the main change of clay minerals is the conversion of kaolinite to analcime. Mass balance calculation indicated during the process of steam stimulation, large quantities of analcime are precipitated with the dissolution of large amounts of quartz, kaolinite, potassium feldspar, and CO₂. These results correlated very well with the experimental results. The calculated results of Liaohe Shuguang Oil Field showed that during the steam stimulation for viscous crude oil, the amounts of minerals dissolved (precipitated) are huge. To control the clogging of pore spaces of oil reservoirs, increased study of water–rock interaction is needed.  相似文献   

Assessment of sand encroachment in Kuwait using GIS     

Anwar B. Al-helal  Jasem M. Al-awadhi 《Environmental Geology》2006,49(7):960-967

Assessment of sand encroachment in Kuwait using Geographical Information System (GIS) technology has been formulated as a Multi-Criteria Decision Making problem. The Delphi method and Analytical Hierarchy Process were adopted as evaluating techniques, in which experts’ judgments were analyzed for objectively estimating and weighting control factors. Seven triggering factors, depicted in the form of maps, were identified and ordered according to their priority. These factors are (1) wind energy; (2) surface sediment; (3) vegetation density; (4) land use; (5) drainage density; (6) topographic change and (7) vegetation type. The factor maps were digitized, converted to raster data and overlaid to determine their possible spatial relationships. Applying a susceptibility model, a map of sand encroachment susceptibility in Kuwait was developed. The map showed that the areas of very high and high sand encroachment susceptibility are located within the main corridor of sand pathway that coincides with the northwesterly dominant wind direction.  相似文献